Cause 1:
Incorrect username and password used on the Windows Share Settings window.

Resolution:
Make sure that the login credentials that are used can log in to the Computer/Server (This is the same as a Windows username or password)
Also check that the user has full read and write permissions on the shared folder

Cause 2:
The shared folder has a space in the name.

Resolution:
We do not recommend including spaces inside folder names. To properly map the shared folder, we recommend renaming the folder by removing any spaces, and to use underscores or hyphens instead. (See image below):